1. Field of the Invention
The present invention relates to a door operator of a rolling door, more particularly to a door operator of a fireproof door which can be shut by rolling-down of door curtain due to its own weight in the event of a fire accident.
2. Brief Description of the Prior Art
Generally, a door operator used in a fireproof rolling door comprises either a failsafe type or a non-failsafe type door operator according to the type of operation. In power interruption condition, the failsafe type door operator releases a brake so as to close the fireproof door at once regardless of the cause of power interruption. In other words, even in the case that the power is not interrupted in the event of a fire accident, the power source can be cut off to release the brake by a fire fighting control device such as a smoke detector, a temperature sensor or the other fire monitoring device so that the door curtain is rolled down due to its own weight to close the door. The main feature of this type lies in that the door can be immediately closed in an event of a fire incident so as to block the fire and the dense smoke from spreading if the power interruption is certainly caused by fire.
In contrast to the above, the non-failsafe type door operator in power interruption condition still keeps the brake in an activated state regardless of the cause of power interruption so that the fireproof door is not shut immediately. Only in the case that the fusible link is melted by a high temperature caused by a fire, the mechanical type brake is actuated mechanically so that the door curtains fall downward due to their own weight to close the door. The main feature of this type lies in that personnel entering/leaving through the fireproof door is not interrupted if the power interruption is caused by non-fire factors.
So far, several documents concerning the failsafe type door operator of fireproof door have been proposed, for example, in U.S. Pat. No. 5,673,514 and U.S. Pat. No. 5,893,234. Basically, two electromagnets are used to maintain a brake device in a braking state under power-on condition, or to release the brake so as to close the door at once in the power interruption state. The structure of this failsafe door operator of fireproof door is very complicated and has a huge volume. On the other hand, documents concerning the non-failsafe door operator of fireproof door such as U.S. Pat. No. 5,203,392 and U.S. Pat. No. 5,386,891 are known to the public, in which either the manual operation of the door operator should be done through mode-switching or a chain is pulled to move a chain disc and at the same time the brake should be released to rotate a rotary shaft. Hence, improvement to use and structure of the conventional art is expected.